Hey Will,

You can apply foliar nitrogen at any stage after emergence as the rates of N are quite low and what doesn’t get on the leaves ends up on the soil anyway.

However, plant uptake of any fraction that lands on a leaf is much more efficient and you get better bang for your buck if you wait until there is a decent amount of leaf matter before starting a foliar application program.

Relevant questions are – do the plants need more nitrogen yet and how many passes you’re prepared to make over the season?

Another consideration is that if you apply too much nitrogen early on you may decommission nitrogen fixing bacteria and compromise the establishment of that microbiome.

Some sort of plant testing helps to inform your decision and again, a bit of leaf growth is required to get a sample, so that’d be a logical starting point.

Agree with everything Mark said. There is some mineralisation of N from organic matter after the break, so adding extra N too early will have less benefit than once the plants are actively growing. The cropping guys work on topping up 4-6 weeks post emergence for winter cereals. If you have kikuyu as a dominant pasture, extra N now with warm soil temps and moisture is beneficial.